Disk storage device having an undercut hub member

ABSTRACT

A disk memory drive includes a brushless drive outer rotor motor having an internal space and a stator with windings. The outer rotor coaxially encircles the stator and a substantially cylindrical air gap is defined between the stator and the rotor. The rotor includes permanent magnets and a hub fixedly connected with the magnet. A disk mounting section is provided on the hub for accommodating at least one storage disk positioned in a clear space, the mounting section being adapted to extend through a central aperture of the storage disk. The windings and the magnets interacting with the windings are disposed for at least half of the axial longitudinal dimension thereof within a space surrounded by the disk mounting section of the hub. Bearings rotatably mount the rotor and the hub.

BACKGROUND OF THE INVENTION

This is a continuation of application Ser. No. 819,099, filed Mar. 4,1997, now U.S. Pat. No. Re. 37,058, issued Feb. 20, 2001, which is acontinuation of application Ser. No. 360,226, filed Dec. 20, 1994, nowabandoned, which is a broadening reissue application of U.S. Pat. No.5,173,814, issued Dec. 22, 1992 from application Ser. No. 653,100, filedFeb. 8, 1991, said application Ser. No. 653,100 being is a continuationof application Ser. No. 07/402,917, filed Sep. 5, 1989, now U.S. Pat.No. 5,001,581, issued Mar. 19, 1991, which is a continuation ofapplication Ser. No. 201,736, filed Jun. 2, 1988, now U.S. Pat. No.4,894,738, issued Jan. 16, 1990, now U.S. Pat. No. Re. 35,792, issuedMay 12, 1998, which is a continuation-in-part of application Ser. No.038,049, filed Apr. 14, 1987, now U.S. Pat. No. 4,843,500, issued Jun.27, 1989, which is a continuation-in-part of application Ser. No.767,671, filed Aug. 21, 1985, now U.S. Pat. No. 4,658,312, issued Apr.14, 1987, which is a continuation of application Ser. No. 412,093, filedAug. 27, 1982, now abandoned, which is a continuation-in-part ofapplication Ser. No. 326,559, filed Dec. 2, 1981, now U.S. Pat. No.4,519,010, issued May 21, 1985, said application Ser. No. 412,093 alsobeing a continuation-in-part of application Ser. No. 244,971, filed Mar.18, 1981, now abandoned, said application Ser. No. 201,736 also being acontinuation-in-part of application Ser. No. 32,954, filed Mar. 31,1987, U.S. Pat. No. 4,779,165, issued Oct. 18, 1988, now U.S. Pat. No.Re. 34,412, issued Oct. 19, 1993, which is a continuation of applicationSer. No. 733,231, filed May 10, 1985, now abandoned, which is acontinuation-in-part of the said application Ser. No. 412,093 .

CROSS-REFERENCE TO RELATED APPLICATIONS

A broadening reissue application for U.S. Pat. No. 5,173,814 was filedon Dec. 20, 1994 and assigned Ser. No. 08/360,226. On Mar. 4, 1997, acontinuation of this application was filed and was assigned Ser. No.08/819,099. On Jun. 9, 1999, five continuation applications from the08/819,099 application were filed. On Nov. 17, 1999, a sixthcontinuation application from the 819,099 application was filed. Theseapplications, as currently pending, are described below:

-   -   a) “Disk Storage Device Having A Sealed Bearing Tube” (Ser. No.        09/333,399, now RE 38,662 ), inventors Elsässer and von der        Heide, filed Jun. 9, 1999;    -   b) “Disk Storage Device Having A Radial Magnetic Yoke Feature”        (Ser. No. 09/333,338; now RE 38,601 ), inventors Elsässer, von        der Heide, and Müller, filed Jun. 9, 1999;    -   c) “Disk Storage Device Having A Hub Sealing Member Feature”        (Ser. No. 09/333,397 ), inventors Elsässer and von der Heide,        filed Jun. 9, 1999;    -   d) “Disk Storage Device Having An Underhub Spindle Motor” (Ser.        No. 09/333,396; now RE 38,178 ), inventors Elsässer, von der        Heide, and Müller, filed Jun. 9, 1999;    -   e) “Disk Storage Device Having a Particular Magnetic Yoke        Feature” (Ser. No. 09/333,400; now RE 38,179 ), inventors        Elsässer and von der Heide, filed Jun. 9, 1999; and    -   f) “Disk Storage Device Having An Undercut Hub Member” (Ser. No.        09/441,504 ), inventors Elsässer and von der Heide, filed Nov.        17, 1999.

The invention relates to a disk storage drive for receiving at least onestorage disk having a central opening, with an outer rotor type drivingmotor having a rotor casing mounted by means of a shaft in a bearingsystem so as to rotate relative to a stator and on which can be placedthe storage disk for driving by the rotor casing, as described in U.S.patent application Ser. No. 353,584, now U.S. Pat. No. 4,438,542, issuedMar. 27, 1984.

The content of this patent is incorporated herein by reference to avoidunnecessary repetition. It relates to a storage drive for receiving atleast one storage disk having a central opening. The driving motorextends coaxially at least partly through the central opening of thestorage disk, and means are provided for connecting the storage disk andthe driving motor rotor.

BRIEF SUMMARY OF THE INVENTION

One problem of the present invention is to further simplify theconstruction of a disk storage described in the aforementioned U.S. Pat.No. 4,438,542, while improving its operation. For example, the storagedisk is to be reliably protected against undesired influencing by themagnetically active parts of the driving motor. In addition, aparticularly space-saving and robust construction of the driving motorare to be achieved.

According to the invention, this first problem is solved in that atleast the part of the rotor casing receiving the storage disk is madefrom a non-ferromagnetic material and carries the shaft directly or bymeans of a hub and in that a magnetic shield made from a ferromagneticmaterial in the form of a drawn can projects into the storage diskreceiving part of the rotor casing and is connected thereto. Theshielding surrounds the periphery of the magnetically active parts ofthe driving motor and also envelops the parts at one end. The shield hasa central opening whose edge is directly radially adjacent the shaft orparts of the driving motor carrying or supporting the shaft. A rotorcasing constructed in this way can be easily manufactured, and iteffectively protects the magnetically sensitive storage disks,particularly magnetic hard storage disks, against magnetic stray fluxemanating from the magnetically active parts of the driving motor. Theshield is preferably in the form of a deep-drawn can, and the part ofthe rotor casing receiving the storage disk can be made from alightweight metal by die casting.

If, in the manner described in the aforementioned U.S. Pat. No.4,438,542, the driving motor is constructed as a brushless directcurrent motor with a permanent magnet rotor, then in accordance with afurther development of the invention a printed circuit board with atleast one rotary position detector and perhaps other electroniccomponents for the control and regulation of the driving motor aremounted on the side of the stator remote from the closed end of theshielding can. This ensures that the rotary position detector and anyfurther circuit components of the magnetic shielding arrangement do notinterfere with the rotating parts.

Further advantageous developments of the invention also are disclosed,including features that contribute to a compact construction of the diskstorage drive. In connection with disk storage drives of the presenttype, high demands are made on the concentricity of the storage disks.It is therefore generally necessary to machine the storage diskreceiving part or to work it in some other way so that it isdimensionally true. As a result of other features of the invention, thenecessary machining is reduced to a relatively small part of thecircumferential surface of the storage disk receiving part and atrouble-free engagement of a storage disk on the shoulder of the storagedisk receiving part is permitted.

Other features of the invention provide a robust precision mountingsupport for utilizing the available axial overall length for maximizingthe distance between the bearings; and permit particularly largedistances between the bearings where the axial installation area betweena mounting or assembly flange and the end of the storage disk receivingpart is limited. Installation space is available on the other side ofthis flange. Still other features provide for alternative solutionsleading to particularly small radial runouts of the rotor; ensure aspace-saving housing of the circuit board; and for solutions whereimportance is attached to a particularly shallow construction.

In a further development of the invention, a disk storage drive of thetype disclosed in U.S. Pat. No. 4,779,165, issued Oct. 18, 1988, nowU.S. Pat. No. Re. 34,412, issued Oct. 19, 1993 is considered. Some suchdisk storage drives have stationary shafts and a sealed off internalspace within the motor.

In the construction of such data storage disk drives with stationaryshafts, problems also have arisen in the following areas:

-   a) Achieving extremely high level of precision required for    repeatable shaft runout;-   b) Improving the sealing of the clean chamber; and-   c) Achieving a and b within acceptable costs.

Yet another purpose of the present invention, therefore, is to provide afurther development of the data storage disk drive of the above typehaving a stationary shaft by providing viable solutions for variouscombinations of the above problems, such as a and c; b and c; and a, band c.

If the rotational position sensor device has several rotational positionsensors, preferably of the type sensitive to magnetic fields, it isadvantageous for these sensors to be supported on a common molded piece,especially if it is made by injection molding. The construction of themolded piece for the accommodation of several rotational positionsensors in accordance with the invention simply ensures the precisemutual alignment of these sensors.

If required, the rotary position sensing arrangement can be mounted on aprinted circuit board, together with any known type of commutationelectronics. This printed circuit board can be supported on a fixedflange or bracket which is, in turn, connected to the shaft throughwhich the connecting leads to the rotary position sensors may be broughtout.

The control arrangement, which preferably takes the form of a controlmagnet device, can be mounted on the outside of a cover which seals offthe space inside the motor. This cover may preferably serve as a bearingbracket as well. The control arrangement, however, also can be mountedon a part of the hub at a distance from the disk carrier stage outsidethe sealed internal space of the motor. A flange which serves to supportthe data storage disk or disks, may be connected to the remaining hubparts as one piece, or alternatively, this flange may form part of thecover which seals off the internal space of the motor.

In accordance with one variant of the present invention, at least theelectric supply leads to the stator windings are brought out of thesealed internal space of the motor over a bearing support ring. Thisarrangement obviates the need to provide passages in the shaft toaccommodate the winding connections. In yet another alternativearrangement, the rotary position sensing arrangement, together with thecommutation electronics, if necessary, can both be housed in the sealedinternal space of the motor with their leads and connections beingbrought out over the bearing support ring. In any event, none of theabove arrangements requires the provision of passages formed through thestationary shaft, thus avoiding the need to weaken the shaft or toperform additional machining operations in the manufacturing thereof.

The bearing support ring can be a prefabricated component provided withrecesses for the passage of the electric leads and connections.Alternatively, the aforesaid connections can be potted in situ insidethe bearing support ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative tonon-limitative embodiments and the attached drawings, wherein:

FIG. 1 is a vertical partial sectional view through an embodiment of theinvention along the line I—I of FIG. 2;

FIG. 2 is a plan view of the arrangement of FIG. 1;

FIG. 3 is a sectional view through another embodiment of the inventionwith an extended bearing tube;

FIG. 4 is a sectional view through a further embodiment of theinvention;

FIG. 5 is a section through a disk storage drive motor, less the hub,according to the invention along line V—V of FIG. 6;

FIG. 6 is a section along line VI—VI of FIG. 5 and illustrating arotational position sensor device located outside the sealed internalspace of the motor;

FIG. 7 is a section similar to FIG. 6 of a modified embodiment of theinvention;

FIG. 8 is a section similar to FIG. 6 of another modified embodiment ofthe invention;

FIG. 9 is a section similar to FIG. 6 of yet another modified embodimentof the invention;

FIG. 10 is a section similar to FIG. 6 of yet another embodiment of theinvention;

FIG. 11 is a section through a disk storage drive according to theinvention illustrating a rotational position sensor device locatedinside the sealed internal space of the motor with leads brought outthrough bearing support ring;

FIG. 12 is a partial section similar to but yet a variant of FIG. 7 ofyet another embodiment of the invention having the rotational positionsensor device located outside the sealed internal space of the motor;

FIG. 13 is a section illustrating a further variant of the embodimentshown in FIG. 6; and

FIG. 14 is a section illustrating yet another variant of the embodimentshown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disk storage drive illustrated in FIG. 1, having an extremelyshallow construction, has a brushless direct current motor 45 having arotor casing 47 fixed to and coaxial with a rotor shaft 46. A statorlamination 48, carrying a stator winding 49, is mounted on a bearingtube 50. The rotor shaft 46 is rotatably mounted within the bearing tube50 by means of two bearings 52 and 53. These are kept axially spaced bya pair of retaining rings 54. A cup spring 55 is supported on theunderside of the bearing 53 by a retaining ring 56 resting on the rotaryshaft 46, so that the bearings 52, 53 are axially braced relative to oneanother. The bearings 52, 53 are pressed into the bearing tube 50 at thetime of assembly. Together with an assembly flange 24, the bearing tube50 forms a one-piece die casting.

The rotor casing 47 comprises a storage disk receiving part 25 and ashielding can 26, which are joined together, for example, by riveting.The storage disk receiving part 25 is made from a non-ferromagneticmaterial, preferably lightweight metal. The rotor shaft 46 is pressedinto a central opening of the storage disk receiving part 25. As analternative, the shaft can be cast into the receiving part.

The shielding can 26 is made from a ferromagnetic material and can inparticular be constructed as a soft iron deep-drawn part. A plurality ofpermanent magnetic segments or a one-part permanent magnet 69 are fixedto the inner face of shielding can 26 radially facing the statorlamination 48. The permanent magnet 69 preferably comprises a mixture ofhard ferrite, for example, barium ferrite, and an elastic material.Thus, it is a so-called rubber magnet. The latter is trapezoidally orapproximately trapezoidally radially magnetized via the pole pitch in amotor construction having a relatively small pole clearance. At the sametime, the shielding can 26 forms the magnetic return path for magnet 69.The shielding can 26 surrounds the magnetically active parts 48, 49, 69of the driving motor 45 on the periphery thereof, as well as on one endthereof. The bottom 28 of shielding can 26 is adapted to the shape ofthe coil winding heads 27 of the stator winding 49 and contains acentral opening 29, whose edge is in the immediate radial vicinity ofthe circumferential surface of the bearing tube 50. In this way, theshielding can effectively prevents the magnetic flux from strayingtowards the outside of the storage disk receiving part 25.

The storage disk receiving part 25 has two stepped stages 74 and 75,each of whose circumferential surfaces in the present embodiment carry aplurality of radially distributed and projecting bearing webs 79 or 80.The outsides of bearing webs 79, 80 are ground in a dimensionally truemanner to accommodate the internal diameter of the hard storage disks tobe placed on the receiving part 25. The stepped stages 74, 75 formshoulders 81, 82 and are provided respectively with an annular recess 83and 84 at the foot axially of bearing webs 79, 80. This structureensures that storage disks mounted on the bearing webs 79, 80, andhaving either one of two opening diameters, will cleanly engage againsteither the shoulder 81 or 82.

The assembly flange 24 is provided with a recess 85 in which is housed aprinted circuit board 86. This printed circuit board carries a rotaryposition detector, for example a Hall IC, as well as other circuitcomponents for the control and regulation of the driving motor 45. TheHall IC 63 extends up axially from the circuit board 86 to the immediatevicinity of the stator lamination 48. The permanent magnet 69 projectsaxially over the stator lamination 48 in the direction of circuit board86 until it partly overlaps the Hall IC 63. In this way, the Hall IC 63or, if desired, some other magnetic field-dependent semi-conductorcomponent, determines the rotary position of the rotor of the drivingmotor 45.

In the illustrated embodiment, the two bearings 52, 53 are spacedapproximately the same axial distance from the axial center of thepermanent magnet 69 and the stator lamination 48.

Disk storages are most usually operated in “clean chamber” environmentsto protect them against contaminants. By means of the assembly flange24, the storage drive is arranged on a partition (not shown) whichseparates the ultra-clean area for receiving the storage disks from theremainder of the interior of the equipment. Dirt particles, greasevapors and the like from bearing 52 and parts of the driving motor 45are prevented from passing into the storage disk receiving area bylabyrinth seals 90 and 91. The labyrinth seal 90 is formed in the end ofthe bearing tube 50 away from the assembly flange 24 that projects intoan annular slot 87 on the inside of the storage disk receiving part 25,accompanied by the formation of sealing gaps. Similarly, for forming thelabyrinth seal 91, the end of the shield can 26 projects into theannular slot 88 of the assembly flange 24. The labyrinth seals 90, 91are preferably dimensioned in the manner described in the aforementionedU.S. Pat. No. 4,438,542.

The embodiment of FIG. 3 differs from the arrangement according to FIGS.1 and 2 in that storage disks having the same opening diameters areplaced on bearing webs 79 of a storage disk receiving part 89, whichsurrounds the majority of the axial dimension of the magnetic shieldingcan 26. In other words, the magnetically active parts 48, 49, 69 of thedriving motor 45 are partially located within the central opening of thestorage disk. A bush-like hub 98 is pressed or cast into the storagedisk receiving part 89. The rotor shaft 46 is then pressed into the hub98. The edge of the central opening 29 in the bottom 28 of the shieldingcan 26 extends up to the portion 99 of the receiving part 89 whichreceived the hub 98.

The bearing tube 50 projects in the axial direction on the side of theassembly flange 100 remote from the stator lamination 48. As a result, aparticularly large axial spacing between the two bearings 52, 53 can beachieved. Axially, bearing 52 is in the vicinity of the axial center ofthe permanent magnet 69 and of the stator lamination 48. The axialspacing between bearings 52 and 53 is equal to or larger than double thebearing external diameter. To prevent electrical charging of the rotorwhich in operation rotates at high speed and which would disturb theoperational reliability of the disk storage device, the rotor shaft 46is electrically conductively connected to the equipment chassis by meansof a bearing ball 78 and a spring contact (not shown). The printedcircuit board 101, carrying the rotary position detector 63 and theother electronic components, is supported on the end of a spacer ring102 facing an assembly flange 100 and is located between the flange andthe stator lamination 48. An annular slot 103 is formed in assemblyflange 100 and is aligned with the annular circuit board 101. Theannular slot 103 provides space for receiving the wire ends and solderedconnections projecting from the underside of the circuit board 101.

FIG. 4 shows an embodiment in which a storage disk receiving part 105 isaxially extended in order to be able to house a larger number of storagedisks than in the arrangement of FIG. 3. The bearing tube 50 iscorrespondingly axially extended in order to be able to use the existinginstallation space with a view to a maximum axial spacing between thebearings 52 and 53. The end of the bearing tube 50, remote from anassembly flange 106, embraces the hub 98 connecting the receiving part105 and the shaft 46, accompanied by the formation of a labyrinth seal107. The edge of the central opening 29 of shielding can 26 extends upclose to the outside of the bearing tube 50. The free end of theshielding can 26 engages a recess 108 in the assembly flange 106. As aresult, a further labyrinth seal 109 is formed. This embodimentotherwise corresponds to the structures already described herein.

In FIGS. 5 and 6, a brushless drive motor, designated as 110 has astator 111 with a stator lamination stack 112. The stator laminationstack 112 is arranged radially and symmetrically with respect to acentral axis of rotation 113 and forms six stator poles 114A to 114F inan essentially T-shaped configuration as seen from above in accordancewith FIG. 5, which poles are positioned at regular angular intervals of60°. Instead of one lamination stack, for example, a sintered iron corecan also be provided. Pole shoes 115A to 115F, together with a permanentmagnetic rotor magnet 116 define an essentially cylindrical air gap 117.The rotor magnet 116 is radially magnetized in four poles around itsperiphery as indicated in FIG. 5; that is to say, it has four sections118A to 118D, and, on the internal side of the annular rotor magnet 116toward the air gap 117 there are positioned, in alternating sequence,two magnetic north poles 119 and two magnetic south poles 120. The poles119, 120 have, in the example depicted, a width of substantially 180°-el(corresponding to 90° mechanical). Thus, in the circumferentialdirection of the air gap 117, an approximately rectangular ortrapezoidal magnetization is obtained. The rotor magnet 116 is mounted,typically by bonding, in an outer rotor casing or bell 121 of softmagnetic material, preferably steel, which serves both as a magneticreturn path and as a magnetic shield. The casing 121 and the magnet 116together form an external rotor 122. The rotor magnet 116 can include inparticular a rubberized magnetic unit, or a plastic-bound magnet.Instead of a single-piece magnetic ring, curved magnetic segments canalso be bonded or otherwise attached in the casing 121. Magneticmaterials made from synthetic bonding compounds, a mixture of hardferrite and elastomers, ceramic magnetic materials or samarium cobaltare all particularly suitable as materials for the magnetic ring orsegments.

The stator poles 114A to 114F abut a total of six stator slots 123A to123F. A three-phase stator winding is inserted into these slots. Each ofthe three phases comprises two 1200°-el fractional pitch windings orcoils 124, 125; 126, 127; and 128, 129, each of which is wound aroundone of the stator poles 114A to 114F. Both of the coils of each phase,which are connected in series, lie, as depicted in FIG. 5, in adiametrically opposed manner and are preferably bifilar wound. As can beseen from the schematic depiction in FIG. 5, any overlapping between thecoils 124 to 129 is avoided. This arrangement allows the end turns ofthe windings 130 (FIG. 6) to be kept as short as possible. In thisembodiment of the present invention, optimal filling of the stator slots123A-123F by the windings is achieved. Fasteners are generally notrequired to close the slot openings.

A hub 132, not depicted in FIG. 5, is provided with a cylindrical diskmounting section 131 and preferably is made of a light metal, especiallyaluminum or an aluminum alloy. It is mounted on the outer rotor casing121. One or more storage disks 134, preferably magnetic or optical fixedstorage disks, are provided on the disk mounting section 131, wherebythe disk mounting section 131 extends through the conventional centralaperture 135 of the storage disks. The lowest storage disk in FIG. 6 islocated on a flange 133 of the hub 132 projecting radially outwardly.The data storage disks 134 can be maintained at an axial distance fromeach other by suitable spacers 136 and are secured to the hub 133 bymeans of a tightening device, not depicted, of a known type. In theembodiment shown in FIG. 6, the stator 111, the stator stack 112 and thestator winding (coils 124 through 129) as well as the rotor magnet 116and the outer rotor casing 121 forming the iron shield, are allcompletely encompassed within the space occupied by the storage diskstage 131 on the hub 132.

In a central aperture 137 of a frontal wall 138 of the hub 132, which isrelatively heavy for reasons of stability, are a ball bearing 139 and amagnetic fluid seal 140 on the side of the support which is axiallyoriented away from the drive motor 110. The seal 140 consists of twoannular pole pieces 141, 142, a permanent magnet ring 143 locatedbetween both these pole pieces, and a magnetic fluid (not shown), whichis inserted into an annular gap 144 between the magnetic ring 143 and astationary shaft 145. Seals of this type are known under the designationof “Ferrofluidic Seal”. An internal space 146 is located within themotor and is sealed on the side of the space oriented away from thefrontal wall 138 by means of a motor cover 147, which is inserted intothe outer rotor casing 121 and the hub 132, by means, for example, ofadhesion. The internal space 146 includes the internal parts such as thestator 111 and permanent magnet 116 as well as bearings 139 and 149. Themotor cover 147 abuts with its cylindrical outer edge 247 the lower edgeof the rotor casing 121. This allows a particularly easy assembling ofthe cover 147 within the hub 132. For sealing purposes, adhesivematerial 190 is placed in a circumferential groove 191 between the cover147 and the hub 132.

The motor cover 147 is supported on the shaft 145 by means of anadditional ball bearing 149. On the side of the ball bearing 149 awayfrom the drive motor 110, there is a magnetic fluid seal 150, which hasa construction corresponding to the seal 140. The seals 140, 150 ensurean effective sealing of the motor internal space 146, including thebearings 139, 149, relative to a clean chamber 148 which accommodatesthe storage disks 134.

The motor cover 147 is provided on the frontal side facing away from thedrive motor 110 with an annular groove 151 receiving a control magnetring 152. The control magnet ring 152 has four sections of alternatingcircumferential magnetization corresponding to the rotor magnets 116,which run in sequence in the circumferential direction and extend over90°, so that alternating north and south poles, aligned with poles 119,120 in the circumferential direction, are provided on the bottom side ofthe control magnetic ring 152.

A stationary flange 154 is disposed on the lower end of the shaft 145 inFIG. 6. The flange 154 is provided with threaded bores 192 for receivingfastening screws by which the disk storage drive may be connected to thedisk drive frame, for example, over a wall delimiting the clean chamber148, or the like. The flange 154 supports a printed circuit board 155 onits frontal side relative to the motor cover 147. Three rotationalposition sensors 156, 157, 158 are mounted on the printed circuit board155. In the embodiment shown, these magnetic field sensors may be Hallgenerators, Hall-IC's, magnetically controlled photocells, magneticdiodes, or the like, which interact with the control magnet ring 152.The rotational position sensors 156, 157, 158 are suitably positioned inthe circumferential direction with regard to the coils 124 to 129 sothat the changes of the sensor switching conditions essentially coincidewith the zero passages of current in the correspondingly positionedcoils. This is attained, in accordance with the embodiment shown in FIG.5, through the fact that the rotational position sensors are displacedby 15-mech with respect to the center of the apertures of the statorslots 123A to 123F. The rotational position sensors 156, 157, 158 may besupported by a common molded part 159 (see, for example, FIG. 14),preferably a plastic injection molded part. By using a common moldedpart 159 as the support for the rotational position sensors, theirrelative positioning with respect to one another can be maintained andreproduced in a particularly precise manner. The printed circuit board155 is fixed to a ring 193 and is tightly pulled against the flange 154by screws 194 screwed into a ring 193. An upwardly projecting outer rim195 of flange 154 defines a hollow cylinder extending into an annulargroove 196 provided in the bottom side of the flange 154. Thereby alabyrinth gap 197 is formed which provides for additional sealingbetween the stationary flange 154 and the rotary motor cover 147.

The connections of the rotational position sensors 156, 157, 158 and/orcommutational electronics likewise positioned on the printed circuitboard are conducted through one or more apertures 161 of the flange 154which open into peripheral cutouts of the ring 193. The connections ofthe stator winding coils 124 to 129 of the drive motor 110 are, on theother hand, conducted outwardly through bores 162, 163 of the stationaryshaft 145 out of the internal space of the disk storage drive, which issealed off by means of the magnetic fluid seals 140, 150. The bores 162,163 can be dimensioned relatively narrowly, because they only have toaccommodate the connections of the stator winding but not theconnections of the rotational position sensors and/or the commutationelectronics (not shown). Furthermore, the rotational position sensors156 to 158 located outside of the sealed space 146 can be closelyadjusted. An excessive weakening of the shaft 145 is thereby avoided.

In a further modified embodiment shown in FIG. 7, the rotor magnet 116is located directly within the hub 132′, which itself forms the magneticshield, and is made of magnetically conductive material, preferably softiron. The control magnet ring 152′ is located on the frontal side of theflange 133 facing away from the disk mounting section 131 of the hub132′, and alternately magnetized in the axial direction. In thisembodiment, the rotational position sensors 156, 157, 158 are axiallyopposed to the control magnet ring 152′. The magnetic fluid seal 150ensures, together with a labyrinth seal 165 which replaces the magneticfluid seal 140 of the embodiment in FIG. 6, the sealing of the internalspace 146, including the bearings 139, 149 relative to the clean chamber148. The connections of the stator winding 166 are conducted through thebores 162, 163 of the stationary shaft 145. It should be understoodthat, even in this embodiment, the rotational position sensors 156, 157,158, can, if desired, be accommodated by a common support correspondingto the molded part 159 (FIG. 14), which support is attached to theprinted circuit board 155.

If it is desirable to manufacture the hub 132′ from magneticallynon-conducting, or poorly conducting, materials, such as light metal oralloy, a separate iron shield can be provided. This can be seen in theembodiment in FIG. 8. There, the rotor magnet 116 is accommodated in aniron shielding ring 167. The flange 169 supporting the storage disk 134forms a part, separated from the hub 132″, of the cover 170 whichaccommodates the ball bearing 149. The hub 132″ and the cover 170 areclosely connected with one another, so that the axial end section of thehub 132″, which extends towards the cover 170, engages in an annulargroove 171 of the cover 170.

In both embodiments of FIGS. 9 and 10, the control magnet ring 152′ islocated in a groove 173 of a bearing support ring 174 on the end of thehub 132. The hub 132 itself forms the magnetic shield, and isaccordingly made from conductive material, particularly steel. Thecontrol magnet ring 152′ interacts, as shown in FIG. 7, with therotational position sensors 156, 157, 158, which are not shown in FIGS.9 and 10. In the embodiment in FIG. 9, the internal space 146 is sealedoff by means of the magnetic fluid seals 140, 150, but in the embodimentin FIG. 10, labyrinth seals 175 are provided in their place. Theembodiment of FIG. 10 further differs from that of FIG. 9 by thestationary shaft 145′ in the area where it supports the statorlamination stack 112, and the area directly adjoining the same axially,being axially thickened so that the shaft 145 forms shoulders 176, onwhich the ball bearings 139, 149 are supported.

In the embodiments shown in FIGS. 8, 9, and 10, the connections of thestator winding are, in a manner preferably corresponding to theembodiments shown in FIGS. 6 and 7, brought out externally throughrecesses of the shafts 145 and 145′.

FIG. 11 depicts an embodiment similar to that of FIG. 11 of copendingU.S. Ser. No. 733,231, in which a soft magnetic yoke ring 167 isinserted in the hub 132, the latter forming a disk mounting section 132and preferably being made of light metal. Both the rotor magnet 116 andthe control magnet 152′ are accommodated in the inner circumference ofthe yoke ring 167. In this embodiment, the printed circuit board 155together with the rotational position sensors 156, 157, 158 are locatedwithin the space 146 sealed by the magnetic fluid seals 140, 150. Thecircuit board 155 may be suspended from the stator lamination stack 112by supports 178. A bearing support ring 180 is provided for bringingoutwardly the connections 180′ of the stator winding as well as theconnections 180″ of the rotational position sensors 156, 157, 158 and/orof the electronic commutating means which likewise may be mounted on theprinted circuit board 155. The support ring 180 is made of the softmagnetic material, preferably ferromagnetic metal, and surrounds and isfirmly fixed to shaft 145″. The ball bearing 149 and the magnetic fluidseal 150 are disposed between the cover 147′ and the support ring 180.At least one and preferably a plurality of axially extending apertures181 are provided in the support ring 180 for receiving theaforementioned connections. After introduction of the connectionstherein, which together are indicated at 182, the apertures 181 aresealed, e.g. by a potting compound or a mastic. This embodimentcompletely avoids bores in the stationary shaft 145″ and therefore thesolid shaft retains its full strength. The provision of a bearingsupport ring 180 provides for a particularly small eccentricity orrun-out of the rotating members. A soft magnetic shield ring 184 isprovided on the inside of the frontal wall 183 of the hub 132.

The embodiment of FIG. 12 corresponds to that of FIG. 7 with theexception that a connection 166 of the stator winding extends through abearing support ring 185 rather than through the bores in the stationaryshaft 145. The ring 185 surrounds the lower portion of the shaft 145.The ball bearing 149 and magnetic fluid seal 150 are disposed in theannular space between the support ring 185 and the ferromagnetic ring153, which is inserted into hub 132′.

In an embodiment where the rotary position sensors are locatedexternally, the winding leads can also be brought out through an innerbearing support ring encompassing the bearing 149, corresponding to thesupport ring 180 in FIG. 11. Furthermore, in an embodiment provided withan inboard rotary position sensing arrangment similar to that shown inFIG. 11, a bearing support ring 185 according to FIG. 12 mounted on thestationary shaft 145 and supporting the ball bearing 149 on the insidecan be used to bring the connections out to the exterior.

The metal support ring 185 according to FIG. 12 ensures that therotating parts will display particularly limited runout. The magneticfield of the magnetic liquid seal 150 can be contained in either theferromagnetic support ring 185 or the ferromagnetic ring 153.

Instead of providing the bearing support rings 180 or 185 with aperturesthrough which the connections can be brought out, the connections canalso be potted in the bearing support ring directly.

FIG. 13 shows an embodiment similar to that shown in FIG. 6, of which itis only a further development in many respects.

A particular feature of this further embodiment is the provision of aflat air gap between rotational position indicator or magnetic controlring 152 and the rotational position sensor 156. The printed circuitboard 155 is firmly fastened to a stationary flange part 154 with thescrew 194. The outside edge of this flange 154 engages in a disk-shapedring member 147″, which may be the motor cover 147 (FIG. 6) in an axialdirection like a hollow cylinder, so as to provide a labyrinth gap 197acting as an additional seal between the stationary flange 154 and thedisk-shaped ring member 147″. The lower edge of the soft iron outerrotor casing 121 bears on the rotating ring member 147″ whosecylindrical outer edge 244 is more easily inserted in the hub body 132than the arrangement shown in FIG. 6. A mastic 190 is used as thesealant in a peripheral groove between the ring member 147″ and the hub132.

From the user's point of view, the entire motor assembly is fastened byuse of appropriate fasteners in the hole 192. The connecting leads fromthe printed circuit board 155 to the rotational position sensor 156 arebrought out through the passage or bore 161 shown with the disked lines,which extends outwardly from an oblique channel 161′ until it terminatesin the peripheral apertures in the ring 193 which is brought to bear onthe flange 154 by a screw 194.

The ring member 147″ corresponds to the elements described in thevarious embodiments and examples as the covers 170, 147, 147′ and therings 53, 74. Preferably, therefore, only 2 parts are needed tocompletely enclose the inner space 146 of the motor other than thestationary shaft 145 and the bearings 139, 149; namely, the rotor casing132 and the disk-shaped ring member 147″.

FIG. 10 shows a ring 175, somewhat L-shaped in section, which rotatestogether with the outer rotor of the hub, whereby the ring 175encompasses an inner, essentially complementary mating part 165, so thatthe longer leg of the outside part 175 is only separated from thestationary shaft by a narrow gap 275. In combination with the insidemating part 165, this arrangement provides an effective labyrinth seal.This is referenced item 175′ in the lower part of FIG. 10, where thebasic L-shaped section of the seal is indicated by a solid line and thecomplementary mating section is referenced 165′. The effectiveness ofthe labyrinth seal can be enhanced if a projection 175″ on the part 175is provided to project into a recess 165′″, of the complementary part165′. The arrangement may be seen also in the upper part of the drawing.In this way, the need to use a substantially more costly magnetic liquidseal of the type shown in FIG. 9 as items 140 and 150, can be avoided.Of course, the incorporation of a labyrinth seal of this type providedwith these two interlocking L-shaped leg profiles has an independentsignificance in connection with data storage disk drives and is notrequired by the other design features of this motor. As alreadymentioned, the additional recesses 165′″ provide further enhancement ofthe sealing action of the labyrinth seals. Elements of this type aremanufactured as large volume extrusions or deep drawn die pressings andtheir cost hardly bears comparison with that of magnetic liquid seals.They provide a good low-cost means of the sealing of the clean chamber,because they can be installed at the points of access to the spaceinside the motor, either in an axial direction or otherwise.

FIG. 14 is a variant of FIG. 6 primarily in the provision of the groove151 in the motor cover 147 which receives the magnet ring 152 and allowsthe rotational position sensor 156 to face the magnet ring across acylindrical air gap vis-a-vis a planar gap in the embodiment shown inFIG. 6.

This invention is not restricted to the use of magnetic field-sensitiverotational position sensors. It can also be used, for example, withoptical sensors.

Although the invention has been described in connection with a preferredembodiment and certain alternatives, other alternatives, modifications,and variations may be apparent to those skilled in the art in view ofthe foregoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications, and variations as fall within thespirit and scope of the appended claims.

1. A disk memory drive comprising: a brushless drive motor having aninternal space defined therein and a stator including winding meansdefining magnetically active parts of the drive motor and having a givenaxial extension, the motor having an outer rotor with an innercircumference, an outer circumference and an open end coaxiallyencircling the stator and a substantially cylindrical air gap definedbetween the stator and the rotor, the rotor including a separate nonferromagnetic hub and a soft iron ring element interiorly of said huband radially located means forming a permanent magnet interiorly of saidring having a predetermined axial extension fixedly connected therewithfor magnetic interaction with said winding means; a disk mountingsection provided on the outside of said hub for accommodating at leastone storage disk for location in a clean chamber surrounding said rotorwhen the drive motor is mounted for operation, the disk mounting sectionon the hub along its axial length being adapted to extend through acentral aperture of the storage disk, the winding means and the magnetmeans interacting therewith being disposed for at least half of theaxial extension thereof within a space surrounded by the disk mountingsection of the hub; and first and second axially separated bearing meanshaving inner and outer races on a shaft rotatably mounting the rotor andthe hub on the shaft, the motor also including rotating meansinteracting with stationary means for determining the rotationalposition of the rotor, the internal space of said motor, which includesthe internal portions thereof with the bearing means, being sealed offagainst the clean chamber when the drive motor is mounted for operation,a disk-shaped ring member being located with precision at the open endof the rotor between the inner circumference of the rotor and the outerrace of one of the axially separated bearing means, and means stationarycontaining leads establishing electrical connection between the internalspace and the outside of the motor.
 2. A disk memory drive according toclaim 1, wherein said rotating means interacting with said stationarymeans comprises rotational position indicator means which includespermanent magnet poles disposed on the disk-shaped ring member forrotation therewith and wherein the rotational position sensor means issensitive to magnetic fields and interacts with the permanent magnetpoles.
 3. A disk memory drive according to claim 2, wherein the shaft isa stationary shaft.
 4. A disk memory drive according to claim 3 whereinthe rotational position sensor means is mounted on a printed circuitboard opposite the disk-shaped member ring.
 5. A disk memory driveaccording to claim 4, further including electronic commutation devicesfor the electromagnetization of the stator also being mounted on theprinted circuit board.
 6. A disk memory drive according to claim 4,wherein the printed circuit board is supported on a flange fixed to thestationary shaft.
 7. A disk memory drive according to claim 3, furtherincluding a magnetic shield means at least circumferentially surroundingthe stator for shielding a clean chamber containing the disk from themagnetic flux of the stator and wherein the stationary shaft is ofconstant diameter and the outer rotor includes a bell-shaped housingwith a substantially closed end and a substantially open end, the statortogether with the magnetic shield being firmly mounted to the stationaryshaft, the inner race of each bearing being firmly mounted on thestationary shaft on either axial side of the stator, the upper bearingbeing positioned inwardly adjacent of the closed end of the bell-shapedouter rotor, and the lower bearing being positioned adjacent the openend of the bell-shaped outer rotor.
 8. A disk memory drive according toclaim 2, wherein the internal space of the motor is sealed by means of acover located at the open end of the outer rotor, the cover also servingas a bearing mounting flange, and the rotational position indicatormeans being mounted on the oustide of the motor cover with respect tothe sealed inner space of the motor.
 9. A disk memory drive according toclaim 2, wherein the outer rotor includes an outer rotor casing offerromagnetic material, the outer rotor serving also as the hub, therotational position indicator being mounted on a lower part of the huboutside the sealed inner space of the motor.
 10. A disk memory driveaccording to claim 2, wherein further comprising a bearing mountingflange having projections in the actual axial direction that projectinto the disk-shaped ring member, and a labyrinth seal located betweenthe projections and the ring member formed by a combination ofcylindrical and radially flat gaps having only dimensions of normalclearances between moving parts.
 11. A disk memory drive according toclaim 10, wherein the projections on the bearing mounting flange arerectangular in section and extend axially.
 12. A disk memory driveaccording to claim 10, wherein the ring member on which part of thebearing race is mounted is substantially flush in the axial directionwith the mounting flange, the ring member being inserted in the outerrotor casing that forms the hub.
 13. A disk memory drive having abrushless drive motor, comprising a stator having a predetermined axialextension, a coaxially positioned outer rotor encircling the stator anddefining therebetween a substantially cylindrical air gap, the rotorhaving an inner circumference and an outer circumference and apredetermined axial extension, a cylindrically shaped permanent magnethaving a predetermined axial extension disposed adjacent the air gap onthe inner circumference of the rotor to rotate therewith andmagnetically interact with the stator, a ferromagnetic hub on the outercircumference of the rotor firmly fixed to the motor magnet, the hubradially surrounding the predetermined axial extension of said permanentmagnet and being provided on its outer circumference with a diskmounting section which can extend through the central opening in astorage disk to mount at least one storage disk thereon, a shaft havingfirst and second axially separated bearing means mounted thereonrotatably mounting the rotor with hub on the shaft, and seals locatedaxially outside of the axial extension of the first and second bearingmeans for sealing the space therebetween.
 14. A disk memory driveaccording to claim 13, wherein the shaft is a stationary shaft.
 15. Adisk memory drive according to claim 14, wherein the seals are magneticliquid seals.
 16. A disk memory drive according to claim 14, wherein theseals are labyrinth seals.
 17. A disk memory drive according to claim14, wherein the stationary shaft projects axially externally of theupper and lower seals.
 18. A disk memory drive according to claim 14,wherein the labyrinth seal is formed of a member having a substantiallyL-shaped cross section, being mounted on and extending radially from thestationary shaft, the short leg of the L-shaped member extending axiallyoutwardly.
 19. A disk memory drive according to claim 16, furtherincluding a ring member of L-shaped cross section being provided on therotor and being opposite and complementary to the stationary mountedL-shaped member, the longer leg of the L-shaped member on the rotorextending inwardly toward the stationary shaft with only a clearancedimension separating the two parts.
 20. A disk memory drive according toclaim 16, wherein the stationary L-shaped member lies inboard axiallyand is substantially encompassed by the rotating L-shaped ring, a flatradial labyrinth gap being formed radially between the respective shortlegs of the L-shaped members.
 21. A disk storage device, comprising incombination: a housing that encloses a clean chamber for providing anenvironment that is maintained substantially contaminant free; at leastone hard magnetic storage disk provided in said clean chamber forrotation about an axis, said at least one disk having a central opening;at least one data head that is provided in said clean chamber and thatallows information to be stored on and read from said at least one hardmagnetic storage disk; a brushless DC motor including a statorconcentric with said axis, a stator winding disposed on said stator, ashaft aligned on said axis, at least one bearing affixed to said shaft,and a rotor that is mounted for rotation about said axis relative tosaid stator, said rotor having a permanent magnetic ring mounted on amagnetically conductive member in a manner such that a generallycylindrical air gap is defined between adjacent surfaces of said statorand said permanent magnetic ring, said brushless DC motor furtherincluding a hub member having a generally cylindrical portion thatextends through the central opening of said at least one disk to mountsaid at least one disk for rotation about said axis in said cleanchamber; wherein said brushless DC motor is mounted in said cleanchamber so that at least a portion of said hub member is contiguous withat least a portion of said rotor and so that the space of said cleanchamber that is occupied by said at least one hard magnetic storage diskis axially separated from the space of said clean chamber that isoccupied by said permanent magnetic ring in a direction along side saidaxis; and wherein said hub member includes a disk support flange that isgenerally perpendicular to said axis and that is contiguous with thegenerally cylindrical portion of said hub member, said hub memberfurther having a generally circular groove formed thereon at a locationclosely spaced adjacent to the portion of said hub member where saidgenerally cylindrical portion of said hub member and said disk supportflange contact each other, said at least one hard magnetic storage diskbeing mounted on said disk support flange.
 22. The disk storage deviceof claim 21 wherein the outside diameter of the generally cylindricalportion of said hub member is smaller than at least one of the distancesspecified in a group consisting of: the outer diameter of said permanentmagnetic ring, the inner diameter of said magnetically conductivemember, and the outer diameter of said magnetically conductive member.23. The disk storage deivce of claim 21 wherein said magneticallyconductive member provides at least a portion of a magnetic return pathfor said permanent magnetic ring.
 24. The disk storage device of claim21 wherein said shaft is rotatable about said axis.
 25. The disk storagedevice of claim 21 wherein said permanent magnetic ring is formed from agenerally radially oriented permanent magnetic material.
 26. The diskstorage device of claim 25 wherein said permanent magnetic ring isradially magnetized to form a plurality of permanent magnets ofalternating polarity, the radial magnetization of said permanent magnetsvaries in a substantially trapezoidal manner in a circumferentialdirection, and a pole gap is defined between the magnetic poles in eachof said permanent magnets such that the circumferential extent of eachpole gap is small compared to the circumferential extent of the magneticpoles in the pair of permanent magnets adjacent thereto.
 27. The diskstorage device of claim 25 wherein said permanent magnetic materialcomprises a mixture of ferrite and an elastic material.
 28. The diskstorage device of claim 21 said hub member comprises a generallynon-magnetically conductive material.
 29. The disk storage device ofclaim 28 wherein said generally non-magnetically conductive materialcomprises a light metal.
 30. The disk storage device of claim 21 whereinsaid generally cylindrical groove is formed in said disk support flange.31. The disk storage device of claim 21 wherein said rotor comprises anexternal rotor.
 32. The disk storage device of claim 21 wherein saidpermanent magnetic ring coaxially surrounds the portion of said statorthat forms said generally cylindrical air gap.
 33. A disk storagedevice, comprising in combination: a housing that encloses a cleanchamber for providing an environment that is maintained substantiallycontaminant free; at least one hard magnetic storage disk provided insaid clean chamber for rotation about an axis, said at least one diskhaving a central opening; at least one data head that is provided insaid clean chamber and that allows information to be stored on and readfrom said at least one hard magnetic storage disk; a brushless DC motorincluding a stator concentric with said axis, a stator winding disposedon said stator, a shaft aligned on said axis, at least one bearingaffixed to said shaft, and a rotor that is mounted for rotation aboutsaid axis relative to said stator, said rotor having a permanentmagnetic ring mounted on a magnetically conductive member in a mannersuch that a generally cylindrical air gap is defined between adjacentsurfaces of said stator and said permanent magnetic ring, said brushlessDC motor further including a hub member having a generally cylindricalportion that extends through the central opening of said at least onedisk to mount said at least one disk for rotation about said axis insaid clean chamber; wherein said brushless DC motor is mounted in saidclean chamber so that at least a portion of said hub member iscontiguous with at least a portion of said rotor and so that the outsidediameter of the generally cylindrical portion of said hub member issmaller than at least one of the distances specified in a groupconsisting of: the outer diameter of said permanent magnetic ring, theinner diameter of said magnetically conductive member, and the outerdiameter of said magnetically conductive member; and wherein said hubmember includes a disk support flange that is generally perpendicular tosaid axis and that is contiguous with the generally cylindrical portionof said hub member, said hub member further having a generally circulargroove formed thereon at a location closely spaced adjacent to theportion of said hub member where said generally cylindrical portion ofsaid hub member and said disk support flange contact each other, said atleast one hard magnetic storage disk being mounted on said disk supportflange.
 34. The disk storage device of claim 33 wherein saidmagnetically conductive member provides at least a portion of a magneticreturn path for said permanent magnetic ring.
 35. The disk storagedevice of claim 33 wherein said shaft is rotatable about said axis. 36.The disk storage device of claim 33 wherein said permanent magnetic ringis formed from a generally radially oriented permanent magneticmaterial.
 37. The disk storage device of claim 36 wherein said permanentmagnetic ring is radially magnetized to form a plurality of permanentmagnets of alternating polarity, the radial magnetization of saidpermanent magnets varies in a substantially trapezoidal manner in acircumferential extent of each pole gap is small compared to thecircumferential extent of the magnetic poles in the pair of permanentmagnets adjacent thereto.
 38. The disk storage device of claim 36wherein said permanent magnetic material comprises a mixture of ferriteand elastic material.
 39. The disk storage device of claim 33 whereinsaid hub member comprises a generally non-magnetically conductivematerial.
 40. The disk storage device of claim 39 wherein said generallynon-magnetically conductive material comprises a light metal.
 41. Thedisk storage device of claim 36 wherein said generally cylindricalgroove is formed in said disk support flange.
 42. The disk storagedevice of claim 36 wherein said rotor comprise an external rotor. 43.The disk storage device of claim 33 wherein said permanent magnetic ringcoaxially surrounds the portion of said stator that forms said generallycylindrical air gap.